The present invention relates to a reduction gear directly joined to a motor, and more particularly is one that relates to the reduction mechanism of a miniature reduction gear of 50 mm maximum diameter that is directly joined to a miniature motor.
FIG. 8 shows an example of a prior miniature reduction gear of this type that uses planetary gears.
In FIG. 8, motor shaft gear 103 is wedged into motor shaft 102 that is in the center of miniature motor 101. Lower case 104 is installed by screw fastening to miniature motor 101 with motor shaft 102 as the central axis. Inner teeth 105 are attached to lower case 104, and there are 2 to 4 planetary gears 106 between them and motor shaft gear 103. Motor shaft gear 103 engages on the inside of plural planetary gears 106, and inner teeth 105 engage on the outside. The centers of plural planetary gears 106 are connected by holder main body 107, and output shaft gear 109 is in the center of holder main body 107. Intermediate cradle 108 is connected to lower case 104, and serves as the bearing for output shaft gear part 109. Output shaft gear 109 engages with planetary gears 106, and planetary gears 106 engage with inner teeth 105. In this manner, the gear that is in the center serves as the motive power, and when we take up to when it rotates holder main body 107 by means of planetary gears 106 as one set, the mechanism repeats the set in any number of stages when the reduction ratio is large. In the final stage of repeating this set, output shaft 110 is in the rotational center of holder main body 107.
Also as shown in FIG. 9, prior miniature reduction gears having a sliding function or a one-way clutch function furnish a sliding mechanism or one-way clutch mechanism on output shaft 110 of miniature reduction gear 121, and transmission is done by transmission gear 123 which is on the said sliding mechanism or one-way clutch mechanism 122.
With such miniature reduction gears using planetary gear mechanisms following the prior constructions shown in FIG. 8 and FIG. 9, the reduction proceeded with holder main body 107 from motor shaft gear 103 via planetary gears 106, but one group of reduction ratios from motor shaft gear 103 to holder main body 107 was small, so it was necessary to have many groups of gears in order to obtain a larger reduction ratio. Because of this, there were problems of cost increases, noise and backlash.
The present invention is one that resolves such prior problems, and its object lies in offering a miniature reduction gear of high transmission efficiency having a miniaturized weight mechanism that takes a sun gear as input and a movable inner gear as output.